Seasonal nearshore sediment resuspension and water clarity at Lake
An extreme sediment transfer event in a Canadian high ... · snow and ice on 2 June (Fig. 2B)....
Transcript of An extreme sediment transfer event in a Canadian high ... · snow and ice on 2 June (Fig. 2B)....
An extreme sediment transfer event in a Canadian high arctic stream Ted Lewis, Carsten Braun, Douglas R. Hardy, Pierre Francus*, Raymond S. Bradley Climate System Research Center, Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, U.S.A. [email protected]. *Present address: Institut national de la recherche scientifique, Centre Eau, Terre et Environnement, 2800 Rue Einstein, Sainte-Foy, Québec G1V 4C7, Canada. RF: T. Lewis, C. Braun, D.R. Hardy, P. Francus and R.S. Bradley
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Abstract
Two large suspended sediment concentration (SSC) pulses were recorded in 1998 in a
small snowmelt-fed stream on Ellesmere Island in the Canadian High Arctic. The second
pulse occurred from 7 to 8 July, when 32% of the monitored seasonal sediment transport
occurred in only four hours. SSC reached 83760 mg L-1, exceeding all previously
recorded values from high arctic glacially-fed and snowmelt-fed rivers by more than one
order of magnitude. The event occurred after the majority of snow in the watershed had
melted, and was preceded by a long period of relatively high air temperature, and a small
rainfall event on 7 July. We consider the most likely cause of the event to be a rapid mass
movement.
Introduction
In a simple arctic snowmelt-fed stream regime, annual suspended sediment yield
is primarily a function of winter snow accumulation and the intensity and duration of
melt (Braun et al., 2000). However, breaching snow dams (Woo and Sauriol, 1981), slush
flows (Braun et al., 2002), aeolian activity (Lewkowicz and Young, 1991), mass
movements (Doran, 1993; Hartshorn, 1995), and large precipitation events (Cogley and
McCann, 1976) can rapidly transport large volumes of fine grained sediment, and these
short-lived events can account for much of the total annual sediment flux. Unfortunately,
most high arctic fluvial monitoring has not been conducted at a sufficiently high temporal
resolution to confidently resolve short term variability in suspended sediment
concentration (SSC; cf. Hardy, 1995), so sediment contributions from large but short-
lived events are poorly documented.
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In this note, we present a high resolution hydrometeorological record for most of
the 1998 melt season from the main river that drains into snowmelt-fed South Sawtooth
Lake (SSL; unofficial name; 79.3oN, 83.9oW; Fig. 1), Fosheim Peninsula, Ellesmere
Island. We focus on the second of two unusual SSC pulses, since it contributed a large
percentage of the 1998 sediment yield. Hydrometeorological measurements were carried
out to provide insight into factors that control sediment flux into the lake, to improve
paleoenvironmental interpretation of the varved lake sediments (cf. Francus et al., 2002).
Site Description
The closest Meteorological Service of Canada (MSC) station to SSL is Eureka (84
km NW; 10 m a.s.l.; Fig. 1). From 1947 to 2001, the average Eureka monthly air
temperature in June, July and August is 2.2, 5.5, and 3.1oC respectively; all other monthly
mean air temperatures are below freezing. Average annual rainfall is 25 mm; respective
mean June, July, and August rainfall totals are 3.7, 11.2, and 8.8 mm. On average,
precipitation occurs on 14 % of days from June to August, but the largest single day of
rain typically accounts for 33% of the annual rainfall total, and daily rainfall totals of up
to 41.7 mm have been recorded.
The area of the SSL stream watershed is 47 km2. Maximum and minimum
elevations are ~915 m (3000 ft) and 280 m (958 ft) a.s.l. (Fig. 1), and the entire watershed
is above marine limit (cf. Bell, 1996). The watershed was probably glaciated in the
Pleistocene (Ó Cofaigh et al., 2000), but is not currently glacierized. There are several
small, possibly perennial, snowbanks in the upper reaches of the watershed.
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Plants and flowers on the Fosheim Peninsula are among the most diverse and
abundant in the High Arctic. Communities are dominated by Salix arctica and Dryas
integrifolia (Edlund and Alt, 1989; Edlund et al., 2000). A partially vegetated paleolake
bed is present immediately above SSL (Fig. 1). Evidence of gelifluction was observed on
slopes slightly above lake level, and shallow debris flow channels are present on steeper
slopes in the northeast and southwest portions of the watershed, and on steep north-facing
slopes adjacent to SSL. Regional permafrost thicknesses are typically about 500 m (Judge
et al., 1981), and thaw depths are usually less than 70 cm during summer (Lewkowicz,
1992).
Two branches of the SSL stream drain the highlands in the northeast and
southwest portions of the watershed. The branches coalesce into a single channel about
1.5 km from SSL, which is incised less than 2 m into unconsolidated paleo-lakebed
sediments (Fig. 1).
Methods
Unless otherwise stated, dates refer to 1998, and regressions use linear fits, with
p<0.0001.
METEOROLOGY
A weather station (Fig. 1) recorded from 27 May 1998 to 10 December 2000. Air
temperature was measured with a Vaiasala HMP45C sensor protected from solar
radiation inside a 12-plate Gill shield. Measurements obtained every minute were stored
as hourly averages on a Campbell Scientific Inc (CSI). model 21x datalogger. An
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unshielded cylindrical precipitation gauge, precise to 0.254 mm, and graduated to 0.2
mm, was placed on the ground, and read several times daily during the 1998 field period.
WATER CONDUCTIVITY
Water conductivity and temperature were measured every 10 seconds at a
hydrometeorological monitoring station (HMS; Fig. 1) using a CSI 247 probe (<± 5%
precision at 25oC from 5 to 440 milliSiemens cm-1 (mS cm-1)). Conductivity was
temperature compensated using synchronously obtained stream water temperatures (mS
cm-1cor; Gardiner and Dackombe, 1983; CSI, 1996). Mean 10-minute values were
recorded with a CSI CR10 datalogger, and were averaged to produce an hourly record
during post-processing.
STAGE
The HMS recorded stage between 12 June and 17 July with two Geokon Model
4850 vibrating wire pressure transducers interfaced with the CR10 datalogger. One
transducer was inside a 5.1 cm diameter slotted stilling well, and the other measured air
pressure changes. Ten-minute mean and standard deviation values were recorded using
measurements made every 20-seconds.
Before the channel was sufficiently ice-free for installation of the HMS, stage was
measured manually using an anchored “offset gauge” with five datums on its shaft, and
the distance between the water surface and the nearest datum was measured. To assess
the precision of the vibrating wire and offset gauges, a manually read staff gauge was
anchored in the stream channel from early June to mid July. Coeval measurements from
the three instruments were assessed, and determined to be intercomparable. Therefore,
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the pre-12 June offset gauge, and 12 June to 17 July HMS records were combined to
produce a continuous log of stage.
DISCHARGE
Stream velocity was measured with a Swoffer Model 2100 flow meter (precision
± 1% from 0.03 to 7.50 m s-1). Discharge measurements were performed manually at
60% of the stream depth using standard measurement techniques (cf. Hardy, 1995). The
rating curve uses discharges between 0.03 and 1.50 m3s-1 (polynomial fit, r2=0.99, n=14,
standard error of estimate=0.06 m3 s-1).
SUSPENDED SEDIMENT CONCENTRATION
Suspended sediment samples were manually obtained near the thalweg using a
US DH-48 depth-integrating sampler. Sample frequency varied from 4 to 15 samples per
day, and volume ranged from 120 to 435 ml. Samples were vacuum filtered on Whatman
Type WCN 0.45 µm papers, and air-dried in the field. Papers were pre- and post-weighed
using balances with precision and reproducibility of ±0.1 mg.
SSC was automatically recorded using a D&A Instruments OBS-3 infrared
backscatterance unit interfaced with the CR10 datalogger. Voltages from the OBS-3 were
calibrated to directly measured SSC (r2=0.93, n=178, slope = 1.48, linear fit). Hourly
averages of SSC were obtained from 15 June to 17 July; however, OBS-3 readings were
spurious on 15, 16 and 27 June, and 7, 8, and 9 July, when overwhelmed by extremely
high SSC, or when organic debris blocked the sensor face. At these times, SSC samples
were obtained manually at a sampling frequency sufficient to adequately resolve diurnal
SSC cycles, which allowed linear interpolation to an hourly resolution.
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Results
Mean daily summer air temperature at SSL was highly correlated with
temperature at Eureka (r2=0.85), but mean daily air temperature was on average 0.9oC
warmer at SSL than at Eureka. Periods of spring and summer precipitation at Eureka and
SSL generally coincided in timing, but not magnitude: 52% less rain fell at Eureka than at
SSL from 4 June to 14 July.
Snowmelt at lower watershed elevations began on 29 May and daily air
temperature rose above freezing on 1 June. Minimal channelized streamflow began on
snow and ice on 2 June (Fig. 2B). Between 4 and 14 June, 65% of the seasonal discharge,
and 45% of the seasonal sediment transfer occurred (Fig. 2B, D). Not including the
second SSC pulse, the highest sustained rates of sediment transfer occurred between 10
and 13 June during a multi-day period of nearly continuous precipitation, when 77% of
the recorded rain fell (Fig. 2A). Discharge dropped sharply on 14 June, after air
temperature at lake level had been decreasing since 9 June, and approached freezing on
13 June and early on 14 June. However, air temperature increased following the morning
of 14 June, and discharge somewhat recovered for about six days.
SSC Pulse I occurred between 18:00 and 21:00 on 27 June (Fig. 3). Unusually
high SSC was recorded (peak hourly SSC=3600 mg L-1), but the event was short lived,
and occurred without exceptional discharge, so it was not responsible for large volumes
of sediment transfer (Fig. 2D). Daily discharge decreased after SSC Pulse I, and distinct
diurnal discharge fluctuations occurred until about 4 July (Fig. 2B).
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SSC PULSE II
SSC Pulse II occurred from 23:00 on 7 July to 22:00 on 8 July. The event had
extremely high SSC, and a rapid and large sediment yield. It occurred late in the melt
season: 90% of the monitored thawing degree-days had been recorded (Fig. 2A). On the
afternoon of 7 July, air temperature decreased from a high of 8.7oC, to a minimum of
1.8oC (Fig. 3A).
On the late evening of 7 July, rain fell relatively intensely at lake level, and sleet
fell at higher watershed elevations. 5.2 mm fell at lake level; the fourth daily largest
rainfall recorded in 1998. At Eureka, a 5.2 mm rainfall event has a 1.2 year recurrence
interval. 4.2 mm of rain, and 12 mm of snow fell at Eureka on 7 and 8 July respectively.
Assuming the rainfall amount recorded at lake level was consistent across the
watershed and was not appreciably stored, about 20% more discharge occurred during
SSC Pulse II than would be expected from rainfall runoff alone. Discharge increased
abruptly on the late evening of 7 July and early morning of 8 July. A secondary discharge
peak occurred at 12:00 on 8 July (Fig. 3B); this was the only time after the period of peak
snowmelt (early-to-mid June) when two distinct discharge peaks occurred in one day.
1.4% of the recorded discharge for the season entered the lake during SSC Pulse II.
Stream water conductivity increased sharply at the beginning the event, staying
around 0.22 mS cm-1cor for nine hours on the morning of 8 July (Fig. 3C). Conductivity
dropped after the morning of 8 July; however, for the remainder of the monitoring period,
conductivity was on average about double the pre-SSC Pulse II mean (Fig. 2C).
Hourly SSC increased from 90 mg L-1 to ~60800 mg L-1 from 22:00 on 7 July to
01:00 on 8 July (Fig. 3). The highest individually measured SSC was ~83760 mg L-1,
sampled at 01:20 on 8 July. 39% of the recorded sediment yield for the entire field
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campaign occurred during SSC Pulse II, representing 610 tonnes (Fig. 2D), or 13 tons
km-2 averaged across the watershed. 32% of the whole season sediment yield occurred in
only four hours. Sediment transfer reached a maximum of 28 standard deviations from
the seasonal mean at 01:00 on 8 July. Discharge and conductivity rises were roughly
synchronous at the beginning of the event; however, discharge increased an hour after
SSC (Fig. 3).
Discussion
Hourly and individually recorded SSC during pulses I and II greatly exceed all
previously published high arctic values from both glacial and nival streams (cf. Hardy,
1995). The highest previously recorded SSC, from the large and highly glacierized
Sverdrup River, Ellesmere Island (Fig. 1) during an exceptional 54.6 mm precipitation
event in 1973 (Cogley and McCann, 1976), is more than an order of magnitude less than
the maximum recorded SSC during SSC Pulse II.
One definition of an extreme hydrologic event is when the measured property is
greater or less than two standard deviations from the mean (Desloges and Gilbert, 1994).
Much of SSC Pulse II greatly exceeds this criterion for sediment transfer, while SSC
Pulse I does not, so the following is a brief assessment of possible triggering events for
SSC Pulse II.
Rainfall Runoff
Rainfall runoff probably contributed to SSC Pulse II. However, the timing of the
event within the melt season was unusual: active layer storage capacity and evaporation
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are typically high later in the melt season, so sediment supply and runoff ratios tend to be
relatively low (Woo and Young, 1997; Woo, 2000).
While the rain on 7 July fell relatively intensely, the rainfall amount was clearly
not exceptional: three larger events were recorded at SSL in 1998. While the Eureka
record predicts a 1.2 year recurrence interval for a 5.2 mm rainfall event, orographic and
continental effects in the Sawtooth Mountains enhance precipitation amounts there
(Lewkowicz and Hartshorn, 1998; Wolfe, 2000; this study), lowering local recurrence
intervals for given precipitation amounts. Also, high arctic MSC stations under-record
true precipitation amounts (Woo et al., 1983).
Snow Dam Collapse and Slush Flows
Meltwater and rainfall runoff could have been dammed behind a perennial
snowbank, and its breach could have initiated SSC Pulse II. Indeed, it appears that more
water ran off during SSC Pulse II than was contributed through precipitation alone.
However, slush flows and snow dam collapses usually occur early in the melt season
(Woo and Sauriol, 1981; Xia and Woo, 1992; Hardy, 1995; Braun et al., 2000). Based on
observations of the watershed, the long time that the stream flowed prior to 8 July, and
the relatively high air temperatures recorded in late June and early July (up to ~14 oC;
Fig. 2A), it is considered unlikely that a snow dam collapse, either within or outside the
stream channel, caused SSC Pulse II. Melting permafrost and residual snowpack could
also have contributed some of the discharge not derived from rainfall runoff.
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Rapid Mass Movement
The series of small late June to early July precipitation events, combined with
consistently high air temperatures (Fig. 2A), likely resulted in increased active layer
thickness, pore water content, and slope instability - ideal conditions for active layer
detachments and blockfalls.
The sharp and sustained increase in stream conductivity that occurred at the
beginning of SSC Pulse II (Fig. 3C), and continued to the end of the monitoring period
(Fig. 2B), is consistent with runoff contacting freshly eroded sediment (cf. Kokelj and
Lewkowicz, 1999). No active debris flows, detachment slides, slumps, or mudflows were
observed; however, a fresh blockfall adjacent to the stream channel might not have been
apparent on the incised stream channel walls, where thermoerosional niching occurs
throughout the melt season.
Rapid mass movements typically occur on the Fosheim Peninsula in mid to late
summer when the active layer is thick, and thaw rates and soil pore water pressures are
high (Hartshorn, 1995; Lewkowicz, 1988; Lewkowicz, 1992; Lewkowicz and Hartshorn,
1998; Lewkowicz and Kokelj, 2002). At three locations on the Fosheim Peninsula
monitored from 1988 to 2000, active layer detachment slides in 1998 were the second
most numerous on record (Brown and Alt, unpublished document).
Concluding Remarks
This study, and analysis of varved sediment cores (Francus et al., 2002), find that
most discharge and sediment transfer into SSL occurs as a result of snowmelt runoff.
However, SSC pulses may confound simple and direct calibrations between
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hydrometeorological variables and varve parameters, since the pulses are likely quasi-
random, interannually variable, and may cause inter- and intrannual disruptions in
sediment supply.
If an active layer mass movement or rainfall-induced runoff triggered either of the
SSC pulses, an increase in their frequency can be expected as summer arctic air
temperatures continue to rise. Active layer thickness is anticipated to increase by 25 to
>50% in the Canadian Arctic Archipelago by 2050 (Anisimov et al., 1997), and sediment
flux to arctic rivers is projected to increase by an average of 22% for every 2oC increase
in regional temperature (Syvitski, 2002).
Finally, we note that SSC pulses I and II could easily have been missed if SSC
was less frequently monitored, or if the monitoring campaign had stopped when
discharge and diurnal discharge fluctuations decreased from late June to early July. If
SSC Pulse II had been missed, the seasonal sediment yield would have been
underestimated by more than 1/3. This underscores the need for high SSC sampling
frequencies over entire melt seasons.
Acknowledgments
This research was supported by an NSF Grant (OPP 9708071) to the University of
Massachusetts. Thanks to Mike Retelle (Bates College) for assistance with fieldwork and
analysis throughout the project, and to Bianca Perren and Whit Patridge for efforts at
SSL. Mindy Zapp noticed the occurrence of SSC Pulse II, and completed many of the
laboratory analyses. The Polar Continental Shelf Project (PCSP) provided superb field
logistics support. This is PCSP contribution #_ and PARCS contribution #_.
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References Cited
Anisimov, O. A., Shiklomanov, N. I., and Nelson, F. E. 1997: Global warming and
active-layer thickness: results from transient general circulation models. Global
and Planetary Change, 15: 241-258.
Bell, T., 1996: The last glaciation and sea level history of Fosheim Peninsula, Ellesmere
Island, Canadian High Arctic. Canadian Journal of Earth Sciences, 33: 1075-
1086.
Braun, C., Hardy, D. R., Bradley, R. S., Zolitschka, B., Retelle, M. J., Smith, S., Lewis,
T., and Francus, P., 2002: What do high arctic fluvial and lacustrine clastic
sediments tell us about climate? Oral presentation at the 37th Annual Northeastern
GSA Section Meeting, Springfield, MA.
Braun, C., Hardy, D. R., Bradley, R. S., and Retelle, M. J., 2000: Streamflow and
suspended sediment transfer to Lake Sophia, Cornwallis Island, Nunavut, Canada.
Arctic, Antarctic, and Alpine Research, 32: 456-465.
Brown, R. D., and Alt, B. T. Unpublished Document. The state of the arctic cryosphere
during the extreme warm summer of 1998: documenting cryospheric variability in
the Canadian Arctic. CCAF Summer 1998 Project Team. A contribution to the
CCAF Science Priority: Arctic Climate Research and Monitoring. pp. 33.
Campbell Scientific, Inc., 1996: 247 Conductivity and Temperature Probes. pp. 11.
Cogley, J. G., and McCann, S. B., 1976: An exceptional storm and its effects in the
Canadian High Arctic. Arctic and Alpine Research, 8: 111-114.
13
Desloges, J. R. and Gilbert, R., 1994: The record of extreme hydrological and
geomorphological events inferred from glaciolacustrine sediments. Canberra
Symposium, 224: 133-142.
Doran, P. T., 1993: Sedimentology of Colour Lake, a nonglacial high Arctic lake, Axel
Heiberg Island, N.W.T., Canada. Arctic and Alpine Research, 25: 353-367.
Edlund, S. A., Alt, B. T., and Garneau, M., 2000: Vegetation patterns on Fosheim
Peninsula, Ellesmere Island, Nunavut. In Garneau, M., and Alt, B. T. (eds.),
Environmental response to climate change in the Canadian High Arctic. Ottawa:
Geological Survey of Canada Bulletin 529, 129-144.
Edlund, S. A., and Alt B. T., 1989: Regional congruence of vegetation and summer
climate patterns in the Queen Elizabeth Islands NWT, Canada. Arctic, 42: 3-23.
Francus, P., Bradley, R. S., Abbott, M. B., Patridge, W., and Keimig, F., 2002:
Paleoclimate studies of minerogenic sediments using annually resolved textural
patterns. Geophysical Research Letters, 29: 1-4.
Gardiner, V. and Dackombe, R. V., 1983: Geomorphological Field Manual. London:
George Allen & Unwin, 254 pp.
Hardy, D. R., 1995: Streamflow and sediment transfer from a mountainous high arctic
watershed, Northern Ellesmere Island. Ph.D. thesis. University of Massachusetts,
Amherst, Massachusetts. 267 pp.
Hartshorn, J., 1995: High energy geomorphic events in the Sawtooth Mountains,
Ellesmere Island, Arctic Canada. M.Sc. thesis. University of Toronto, Toronto,
Ontario. 136 pp.
Judge, A. S., Burgess, M., Taylor, A. E., and Allen, V. S., 1981: Canadian geothermal
data collection - Northern wells 1978-80. Geothermal Service Canada, Earth
14
Physics Branch, Energy Mines and Resources Canada.
http://sts.gsc.nrcan.gc.ca/permafrost/permafrostdatabases/geothermaldatacollectio
n/geothermdatacol.htm.
Kokelj, S. V., and Lewkowicz, A. G., 1999: Salinization of permafrost terrain due to
natural geomorphic disturbance, Fosheim Peninsula, Ellesmere Island. Arctic, 52:
372-385.
Lewkowicz, A. G., 1988: Slope processes. In Clark, M. J., ed. Advances in periglacial
geomorphology. Great Britain: John Wiley & Sons Ltd, 325-368.
Lewkowicz, A.G., 1992: Factors influencing the distribution and initiation of active-
layer detachment slides on Ellesmere Island, Arctic Canada. In Dixon, J.C. and
Abrahams, A.D. (eds.), Periglacial Geomorphology. Proceedings of the 22nd
Annual Binghamton Symposium in Geomorphology. West Sussex: John Wiley &
Sons, Inc, 223-250.
Lewkowicz, A. G., and Hartshorn, J., 1998: Terrestrial record of rapid mass movements
in the Sawtooth Range, Ellesmere Island, Northwest Territories, Canada.
Canadian Journal of Earth Sciences, 35: 55-64.
Lewkowicz, A. G., and Kokelj, S. V., 2002: Slope sediment yield in arid lowland
continuous permafrost environments, Canadian Arctic Archipelago. Catena, 46:
261-283.
Lewkowicz, A. G. and Young, K. L., 1991: Observations of aeolian transport and niveo-
aeolian deposition at three lowland sites, Canadian Arctic Archipelago.
Permafrost and Periglacial Processes, 2: 197-210.
15
Ó Cofaigh, C., England, J., and Zreda, M., 2000: Late Wisconsinan glaciation of southern
Eureka Sound: evidence for extensive Innuitian ice in the Canadian High Arctic
during the Last Glacial Maximum. Quaternary Science Reviews, 19: 1319-1341.
Syvitski, J. P. M., 2002: Sediment discharge variability in Arctic rivers: implications for a
warmer future. Polar Research, 21: 323-330.
Wolfe, P. M., 2000: Glacier hydrology in the Sawtooth Range, Fosheim Peninsula,
Ellesmere Island, Nunavut. In Garneau, M., and Alt, B. T. (eds.), Environmental
response to climate change in the Canadian High Arctic. Ottawa: Geological
Survey of Canada Bulletin 529. 375-390.
Woo, M. -k., 2000: McMaster River and arctic hydrology. Physical Geography, 21: 466-
484.
Woo, M. -k., Heron, R., Marsh, P., and Steer, P., 1983: Comparison of weather station
snowfall with winter snow accumulation in high arctic basins. Atmosphere-
Ocean, 21: 312-325.
Woo, M. -k., and Sauriol, J., 1981: Effects of snow jams on fluvial activities in the High
Arctic. Physical Geography, 2: 83-98.
Woo, M. -k., and Young, K. L., 1997: Hydrology of a small drainage basin with polar
oasis environment, Fosheim Peninsula, Ellesmere Island, Canada. Permafrost and
Periglacial Processes, 8: 257-277.
Xia, Z., and Woo, M. -k., 1992: Theoretical analysis of snow-dam decay. Journal of
Glaciology, 38: 191-199.
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Figure Captions
FIGURE 1. Topographic map of the South Sawtooth Lake watershed (shaded), and
surroundings (lower inset). Topographic contours are from 1:250000 NTS maps 49H:
Cañon Fiord, and 49G: Slidre Fiord. Contour interval is 500 ft a.s.l. (152 m). SSL, South
Sawtooth Lake; Triangle, automated weather station and hydrometeorologic monitoring
stations; Dashed line, paleo lakebed (location estimated visually). Crosses represent
arbitrarily chosen latitude/longitude markers. Upper inset, relative area-elevation curve
for the South Sawtooth Lake watershed.
FIGURE 2. Monitored 1998 hydrometeorological conditions near lake level at South
Sawtooth Lake. A: hourly and mean daily air temperature, thawing degree days and daily
precipitation (inverted Y-axis), B: hourly discharge, cumulative discharge, and hourly
conductivity (inverted Y-axis), C: hourly suspended sediment concentration (SSC), D:
hourly suspended sediment discharge (SSQ, log10 scale), and sediment yield (cumulative
SSQ).
FIGURE 3. Detail of monitored hydrometeorological conditions around suspended
sediment concentration (SSC) pulses I (left series of graphs) and II (right series). Note
the difference in y-axis scales between left and right series of graphs. Gray shading
represents the timing of the two SSC pulses. A: air temperature, B: discharge, C:
conductivity, D: SSC (log10 scale). Cross symbols represent SSC obtained with the DH-
48; other symbols represent hourly averages; dashed lines represent times when the
OBS-3 measurement was outside our measurement range, and hourly SSC was
determined from manually obtained water samples.
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FIG 1: Lewis T., Braun C., Hardy, D.R., Francus, P., Bradley, R.S.
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FIG 2: Lewis T., Braun C., Hardy, D.R., Francus, P., Bradley, R.S.
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12
0x10
1x10
2x10
3x10
4x10
5x10
0.2
0.4
0.6
0.8
1.0
1.2
06:0
0
09:0
0
12:0
0
15:0
0
18:0
0
21:0
0
00:0
0
03:0
0
06:0
0
09:0
0
12:0
0
00:0
0
03:0
0
06:0
0
09:0
0
12:0
0
15:0
0
18:0
0
21:0
0
00:0
0
03:0
0
06:0
0
09:0
0
12:0
0
15:0
0
18:0
0
21:0
0
00:0
0
0.08
0.12
0.16
0.20
0.24
0
2
4
6
8
10
0.0
0.4
0.8
1.2
1.6
00:0
0
03:
00
06:
00
09:
00
12:0
0
15:0
0
18:0
0
21:0
0
00:0
0
03:
00
06:
00
09:
00
12:0
0
15:0
0
18:0
0
21:0
0
00:0
0
oA
ir T
em
pe
ratu
re (
C)
3
-1D
isch
arg
e (
ms
)C
on
du
ctiv
ity (
mS
-1
cm)
cor
Su
spe
nd
ed
Se
dim
en
t-1
Co
nce
ntr
atio
n (
mg
L)
(A)
(B)
(C)
(D)
SSC Pulse I SSC Pulse II
FIG 3: Lewis T., Braun C., Hardy, D.R., Francus, P., Bradley, R.S.
6/27 6/28 7/7 7/8
6/27 6/28 7/7 7/8
1x10
2x10
3x10
4x10
5x10
19TOP